SOLID as OOP abstraction

Paweł KlimczykGemotial 2016

About me

•Software engineer•Running Gemotial Software Studio •Co-organizer of WrocNET•Blog: http://blog.klimczyk.pl•E-mail: pawel@klimczyk.pl•Twitter: @pwlklm•GitHub: pawelklimczyk

Software Quality/SOLIDjobesto.comC#/.NET/BizTalknetdevelopers.pl BJJ

What I do

What is OOP ?

•Abstraction•Encapsulation•Inheritance•Polymorphism

OOP (r)evolution

•Simula 67, Smalltalk •Ada, Lisp•C#, Java

OOP bad habits- Code Smells

• Duplicate Code• Long Method• Comments• Long Parameter List• Large Class• Switch Statements• Parallel Inheritance

Hierarchies• Conditional Complexity• Combinitorial Explosion• Uncommunicative Name• Dead Code• Inconsistent Names• Temporary Field

OOP bad habits - Design Smells• Alternative Classes with

Different Interfaces• Primitive ObsessionData

Class• Data Clumps• Refused Bequest• Inappropriate Intimacy• Indecent Exposure• Feature Envy

• Lazy Class• Message Chains• Middle Man• Divergent Change• Shotgun Surgery • Parallel Inheritance

Hierarchies• Incomplete Library Class• Solution Sprawl

Technical debt trap

•Hard to extend rotten code•The longer we wait to remove the smells, the more it will cost

SOLID – the beginning

Michael Feathers Robert C.Martin

Year ~2000

Occam's razor principleOccam's razor is a problem-solving principle devised by William of Ockham. The principle states that among competing hypotheses, the one with the fewest assumptions should be selected. Other, more complicated solutions may ultimately prove correct, but—in the absence of certainty—the fewer assumptions that are made, the better.

SOLID

•Single Responsibility Principle (SRP)•Open-Closed Principle (OCP)•Liskov Substitution Principle (LSP)•Interface Segregation Principle (ISP)•Dependency Inversion Principle (DIP)

Single Responsibility Principle (SRP)

A class or similar unit of code should have one responsibility only and, therefore, only one reason to change.

Single Responsibility Principle (SRP)

Open-Closed Principle (OCP)

You should be able to extend a classes behavior, without modifying it.

Open-Closed Principle (OCP)

Liskov Substitution Principle (LSP)

Derived classes must be substitutable for their base classes.

Liskov Substitution Principle (LSP)

Interface Segregation Principle (ISP)

Make fine grained interfaces that are client specific.Clients should not be forced to depend upon interfaces that

they don't use.

Interface Segregation Principle (ISP)

Dependency Inversion Principle (DIP)

Depend on abstractions, not on concretions.High level modules should not depend upon low level modules

and abstractions should not depend upon details.

Dependency Inversion Principle (DIP)

Other principles

•Keep It Simple Stupid (KISS)•You Ain’t Gonna Need It (YAGNI)•Don’t Repeat Yourself (DRY)

References

• http://objectmentor.com/Images/photo_feathers.jpg• http://

upload.wikimedia.org/wikipedia/commons/thumb/e/ee/Robert_Cecil_Martin.png/220px-Robert_Cecil_Martin.png

• http://www.butunclebob.com/ArticleS.UncleBob.PrinciplesOfOod• SOLID examples:• https://msdn.microsoft.com/en-us/magazine/dn683797.aspx

Q&A